simply by 'hash intialization' (%$hash_copy = %$hash_ref):

use strict;
use warnings;

my $hash_ref = {
    hack    => 'slash',
    frobozz => 'portrait',
    candle  => 'lit',
};

my $hash_copy;

%$hash_copy = %$hash_ref;
map $_ .= '_mod', values %$hash_copy;   # encouraged in v.5.10

print map "$_ => $hash_ref->{$_}  \n", keys %$hash_ref;
print map "$_ => $hash_copy->{$_} \n", keys %$hash_copy;
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Regards

mwa